FILE - In this Thursday, March 15, 2012 photo provided by Red Bull Stratos, Felix Baumgartner prepares to jump during the first manned test flight for Red Bull Stratos over Roswell, N.M. On Monday, Oct. 8, 2012 over New Mexico, Baumgartner will attempt to jump higher and faster in a free fall than anyone ever before and become the first skydiver to break the sound barrier. (AP Photo/Red Bull Stratos, Jay Nemeth)

His blood could boil. His lungs could overinflate. The vessels in his brain could burst. His eyes could hemorrhage. And, yes, he could break his neck while jumping from a mind-boggling altitude of 23 miles.

But the risk of a gruesome death has never stopped "Fearless Felix" Baumgartner in all his years of skydiving and skyscraper leaping, and it's not about to now.

On Monday over New Mexico, he will attempt the highest, fastest free fall in history and try to become the first skydiver to break the sound barrier.

"So many unknowns," Baumgartner says, "but we have solutions to survive."

The 43-year-old former military parachutist from Austria is hoping to reach 690 mph, or Mach 1, after leaping from his balloon-hoisted capsule over the desert near Roswell.

He will have only a pressurized suit and helmet for protection as he tries to go supersonic 65 years after Chuck Yeager, flying an experimental rocket plane, became the first human to go faster than the speed of sound.

Doctors, engineers and others on Baumgartner's Red Bull-sponsored team have spent as much as five years studying the risks and believe they have done everything possible to bring him back alive. He has tested out his suit and capsule in two dress rehearsals, jumping from 15 miles in March and 18 miles in July.

Baumgartner will be more than three times higher than the cruising altitude of jetliners when he hops, bunny-style, out of the capsule and into a near-vacuum where there is barely any oxygen and less than 1 percent of the air pressure on Earth.

If all goes well, he will reach the speed of sound in about half a minute at an altitude of around 100,000 feet. Then he will start to slow as the atmosphere gets denser, and after five minutes of free fall, he will pull his main parachute. The entire descent should last 15 to 20 minutes.

He will be rigged with cameras that will provide a live broadcast of the jump via the Internet, meaning countless viewers could end up witnessing a horrific accident. Baumgartner is insistent on going live with his flight.

"We want to share that with the world," he says. "It's like landing on the moon. Why was that live?"

The No. 1 fear is a breach of Baumgartner's suit. If it breaks open - if, say, he bangs into the capsule while jumping or supersonic shock waves batter him - potentially lethal bubbles could form in his bodily fluids. That's what's known as boiling blood. A Soviet military officer died in 1962 after jumping from a balloon at 86,000 feet; the visor of his helmet hit the gondola and cracked.

Then there's the risk of a flat spin, in which Baumgartner loses control of his body during the free fall and starts spinning. A long, fast spin, if left unchecked, could turn his eyeballs into blood-soaked orbs, and he could be temporarily blinded. Also, a massive blood clot could form in his brain.

A small stabilizing chute will automatically deploy if he goes into a flat spin and blacks out or otherwise becomes incapacitated. He also has an emergency chute that will automatically deploy if he is unable to pull the cord on his main chute.

If he makes it back in one piece, Baumgartner plans on settling down with his girlfriend, flying helicopters in the United States and Austria, performing mountain rescues and firefighting.

"After this," he promises, "I'm going to retire because I've been successfully doing things for the last 25 years, and I'm still alive."